Substantial human exposure, meaning

Meaning of"Substantial Quantities"or"Substantial Human Exposure"... 

In selecting fields to be studied with priority, the complex pattern of human exposure to unwanted factors will not always mean that all responsible compounds must be known and identified. The knowledge of compounds that inhibit adverse reactions as well as health-promoting compounds is of substantial importance. Increased knowledge of the structure-effect relation of chemicals enables scientists to direct and limit their investigations to compounds of major interest. 

Geneticists commonly turn to current theory to supply such an answer. But relevant theories tend to be poorly substantiated and by no means universally accepted. Thus human data are needed to determine what the mutation-maintained component in human disease is, and any program of monitoring to avert significant human exposure would have to be broad enough to include as a major emphasis this sort of activity. 

Pollutant realism Is achieved when the test system Includes sufficient diversity of components and the physical and chemical properties so that the pollutant behaves In the test system as it would In nature. Pollutant realism Is lacking because, In most test protocols, the pollutant does not Interact with any part of the environment, except the organism. A lack of pollutant realism In traditional tests may result In overestimates of risk. As an example, substantial Information Is now available about the toxicity of TCDD to numerous species when they are exposed via Injection, Incubation, diet, or dermal application. At Times Beach, Missouri, the TCDD is In the soli, and because It has apparently been there for some time, It is probably tightly bound to the soil. Little Is published about the toxicity of TCDD bound to soil, for any means of exposure. Intuitively, I suspect the TCDD Is less toxic when bound to soil than In the forms commonly used In toxicity testing. Thus, the risks of TCDD-lnduced toxicity to humans at Times Beach may be much smaller than would be suggested by the results of traditional testing which lacks this aspect of pollutant realism. 

Potential occupational carcinogen means any substance, or combination or mixture of substances, which causes an increased incidence of benign and/or malignant neoplasms, or a substantial decrease in the latency period between exposure and onset of neoplasms in humans or in one or more experimental mammalian species as the result of any oral, respiratory, or dermal exposure, or any other exposure which results in the induction of tumors at a site other than the site of administration. This definition also includes any substance... 

---